1. Technical Field
The present invention relates to extension rods used with hand tools, and more particularly, to a rotary extension rod.
2. Description of Related Art
For providing various levels of reach and convenient use, many hand tools (such as garden shears) are designed to work with an extension rod so as to be adjustable in length. For example, one prior-art patent owned by the applicant, Taiwan Patent No. M268476, has disclosed an extension rod that uses a knob to control a rotatory member to deflect. When the major-radius portions of the rotatory member press against the inner wall of the positioning ring, the rubber part of the positioning ring abuts against the inner wall of the outer tube and prevents the outer tube from moving with respect to the inner tube, thereby providing positioning effect. When the major-radius portions of rotatory member separate from the inner wall of the positioning ring, the rubber part of the positioning ring leaves from the inner wall of the outer tube, thereby allowing the outer tube to be repositioned as desired.
However, in practical use, the major-radius portions of the rotatory member and the inner wall of the positioning ring hardly contact with each other as expected. As a result, the positioning ring is not effectively opened wide by the rotatory member and the friction to the outer tube is therefore impaired. Consequently, when the outer tube receives a relatively large axial force, the tubes tend to slide and the total length of the inner and outer tubes of the known extension rod is likely to unexpectedly change in use. Hence, the prior art needs to be improved.